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TECHNOLOGY, COMPUTING, AND SIMULATION

Can Mixed Venous Hemoglobin Oxygen Saturation Be Estimated Using a NICO Monitor?

Yoshifumi Kotake, MD, PhD^*, Takashige Yamada, MD, Hiromasa Nagata, MD, Takeshi Suzuki, MD, PhD, and Junzo Takeda, MD, PhD

From the *Department of Anesthesiology, Toho University Medical Center Ohmori Hospital; and Department of Anesthesiology, School of Medicine, Keio University, Tokyo, Japan.

Address correspondence to Yoshifumi Kotake, MD, PhD, Department of Anesthesiology, Toho University Medical Center Ohmori Hospital, 6-11-1, Ohmori-nishi, Ohta, Tokyo 143-8541, Japan. Address e-mail to ykotake{at}med.toho-u.ac.jp.

BACKGROUND: We hypothesized that mixed venous hemoglobin oxygen saturation (SvO₂) can be estimated by calculation from CO₂ production, cardiac output, and arterial oxygen saturation measured using a noninvasive cardiac output (NICO) monitor (Novametrix-Respironics, Wallingford, CT).

METHODS: Twenty-three patients undergoing aortic aneurysm repair underwent SvO₂ monitoring using a pulmonary artery catheter and cardiac output monitoring using a NICO monitor. The estimated SvO₂ value calculated from NICO monitor-derived values was compared with the SvO₂ value measured using a pulmonary artery catheter. The accuracy of this estimation was analyzed with Bland-Altman method. The ability of this estimation to track the change of SvO₂ was also evaluated using correlation analysis to compare the changes of estimated SvO₂ and measured SvO₂.

RESULTS: The bias ± limits of agreement of the estimated SvO₂ against measured SvO₂ was –2.1% ± 11.2%. The change of estimated SvO₂ was modestly correlated with the change of measured SvO₂.

CONCLUSIONS: SvO₂ derived from the values measured by the NICO monitor cannot be used interchangeably with the values measured spectrophotometrically using the pulmonary artery catheter. More refinement is required to obtain more reliable estimate of SvO₂ less invasively. However, large changes of SvO₂ may be detected with this method and can be used as a precautionary sign when the balance between oxygen supply and demand is compromised without inserting a central venous catheter.